The 'Automatic' hitmaker admits that the pounds didn't leave automatically; she had to really work to shed them -- which she did to tunes of the one and only Spears! Lambert tells Women's Health magazine that she finds inspiration during her workouts by listening to Spears and picturing her sleek, toned body.

"Like if I put on Britney, I can picture Britney's body and I'm like, 'Oh! Faster!'" the star shares.

When the Princess of Pop found out about Lambert's inspiration from her younger sister, country newcomer Jamie Lynn Spears, she just couldn't sit quietly. "My sister @jamielynnspears just showed me. You look amazing!!" Spears wrote on Instagram, tagging the country singer.

Lambert first debuted her slimmer figure at the 2013 CMA Awards, which was right around her 30th birthday. Even with all of her hard work in the gym, there was one thing she refused to give up: drinking.

“I didn’t give up drinking. I refused. You have to drink to put up with my husband!” Lambert says, laughing.

We'd bet there are plenty of country fans who put on Lambert's music, picture her body and run a little bit faster. She's an inspiration!